YafaRay Plug-in - reviewing for Yafaray 3.0

[micheus]

One thing is the user preferences that is reused for any project and other is the project values/prefs (if we can say this way) that will be remembered when reloading it.

I was thinking about the last one, because the preferences by plugin was implemented in older than v2.* by using a button in the dialogs (save default) - something that we couldn't yet enable using the new wx GUI.